1，创建Servlet
package Test;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Random;
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class Servlet174 extends HttpServlet {
/**
* Constructor of the object.
*/
public Servlet174() {
super();
}
/**
* Destruction of the servlet. <br>
*/
public void destroy() {
super.destroy(); // Just puts "destroy" string in log
// Put your code here
}
/**
* The doGet method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to get.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doPost(request, response);
}
/**
* The doPost method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to post.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public Color getRandomColor(int fc,int bc){
Random random = new Random();
Color randomColor = null;
if(fc>255) fc=255;
if(bc>255) bc=255;
//设置个0-255之间的随机颜色值
int r=fc+random.nextInt(bc-fc);
int g=fc+random.nextInt(bc-fc);
int b=fc+random.nextInt(bc-fc);
randomColor = new Color(r,g,b);
return randomColor;//返回具有指定红色、绿色和蓝色值的不透明的 sRGB 颜色
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//禁止页面缓存
response.setHeader("Pragma", "No-cache");
response.setHeader("Cache-Control", "No-cache");
response.setDateHeader("Expires", 0);
response.setContentType("image/jpeg"); //设置响应正文的MIME类型为图片
int width=60, height=20;
/**创建一个位于缓存中的图像，宽度60，高度20 */
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
Graphics g = image.getGraphics(); //获取用于处理图形上下文的对象，相当于画笔
Random random = new Random(); //创建生成随机数的对象
g.setColor(getRandomColor(200,250)); //设置图像的背景色
g.fillRect(0, 0, width, height); //画一个矩形 ，坐标（0，0），宽度60，高度20
g.setFont(new Font("Times New Roman",Font.PLAIN,18)); //设定字体格式
g.setColor(getRandomColor(160,200));
for(int i=0;i<130;i++){ //产生130条随机干扰线
int x = random.nextInt(width);
int y = random.nextInt(height);
int xl = random.nextInt(12);
int yl = random.nextInt(12);
g.drawLine(x,y,x+xl,y+yl); //在图象的坐标（x,y）和坐标（x+x1,y+y1）之间画干扰线
}
String strCode="";
for (int i=0;i<4;i++){
String strNumber=String.valueOf(random.nextInt(10)); //把随机数转换成String字符串
strCode=strCode+strNumber;
//设置字体的颜色
g.setColor(new Color(15+random.nextInt(120),15+random.nextInt(120),15+random.nextInt(120)));
g.drawString(strNumber,13*i+6,16); //将验证码依次画到图像上,坐标（x=13*i+6,y=16）
}
request.getSession().setAttribute("Code",strCode); //把验证码保存到Session中
g.dispose(); //释放此图像的上下文以及它使用的所有系统资源
ImageIO.write(image, "JPEG", response.getOutputStream()); //输出JPEG格式的图像
response.getOutputStream().flush(); //刷新输出流
response.getOutputStream().close(); //关闭输出流
}
/**
* Initialization of the servlet. <br>
*
* @throws ServletException if an error occurs
*/
public void init() throws ServletException {
// Put your code here
}
}
2，创建用于显示验证码的JSP
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>用户注册</title>
</head>
<body>
<form action="" method="post">
<img alt="" src="validatecode" >
</form>
</body>
</html>
3，结果
